1. Field of the Invention
The present invention relates to an improved torque measuring apparatus particularly suitable for use in non-contact measurement of torque transmitted through a rotating shaft of ferromagnetic material.
2. Description of the Prior Art
In various rotary drive systems, it is important that a transmitted torque can be measured accurately and simply. The accurate measurement of torque is very desirable for analysis or grasp of running drive systems used in various fields of industry.
Generally, such rotary drive systems includes various prime movers such as automobile engines, electric car motors, industrial motors and so on. Analysis of the running prime movers requires accurate measurement of torque in addition to revolution.
Particularly, the vehicle engines can properly be controlled relating to their ignition timing, fuel injection, gearshift timing or gear ratio by measuring torques in the power train consisting of engine, transmission, propeller shaft, gear wheels and so on. The measurement of torque serves to improve fuel consumption or running characteristics.
It has been desired to develop a small-sized apparatus which can steadily measure torques over a wide range of revolutions.
In the rotary drive systems, it is known that a rotating shaft for transmitting torques has a strain created therein, which is proportional to the transmitted torque. Thus, the level of the transmitted torque can be known by measuring such a strain.
A torque measuring system for detecting a strain created in a rotating shaft by the use of magnetostriction effect is well-known, for example, from "ASEA Journal" 1960, Vol. 33.3, pp 23-32 or SEA 820904. A portion of the rotating shaft for transmitting the torques is formed of ferromagnetic material. Non-contact measurement of torque is accomplished by measuring the strain in the rotating shaft by the use of a magnetic sensor.
FIGS. 4 and 5 of the accompanying drawings schematically show a prior art torque measuring apparatus on a rotating shaft 10 in a vehicle engine. FIG. 4 is a schematic side view of the torque measuring apparatus while FIG. 5 is a schematic cross-section taken along a line V--V in FIG. 4.